diff --git a/net/tcp/tcp_conn.c b/net/tcp/tcp_conn.c
index d7a80706764..6251cadcfa4 100644
--- a/net/tcp/tcp_conn.c
+++ b/net/tcp/tcp_conn.c
@@ -155,8 +155,8 @@ static inline FAR struct tcp_conn_s *tcp_ipv4_listener(in_addr_t ipaddr,
  ****************************************************************************/
 
 #if defined(CONFIG_NET_IPv6) && defined(CONFIG_NETDEV_MULTINIC)
-static inline FAR struct tcp_conn_s *tcp_ipv6_ listener(net_ipv6addr_t ipaddr,
-                                                        uint16_t portno)
+static inline FAR struct tcp_conn_s *
+tcp_ipv6_listener(const net_ipv6addr_t ipaddr, uint16_t portno)
 {
   FAR struct tcp_conn_s *conn;
   int i;
@@ -436,7 +436,7 @@ static inline FAR struct tcp_conn_s *
   FAR struct tcp_conn_s *conn;
   net_ipv6addr_t *srcipaddr;
 #ifdef CONFIG_NETDEV_MULTINIC
-  net_ipv6addr_t destipaddr;
+  net_ipv6addr_t *destipaddr;
 #endif
 
   conn       = (FAR struct tcp_conn_s *)g_active_tcp_connections.head;
@@ -575,10 +575,16 @@ static inline int tcp_ipv6_bind(FAR struct tcp_conn_s *conn,
   /* Verify or select a local port */
 
 #ifdef CONFIG_NETDEV_MULTINIC
+  /* The port number must be unique for this address binding */
+
   port = tcp_selectport(PF_INET6,
-                        (FAR const union ip_addr_u ipaddr *)addr->sin6_addr.in6_u.u6_addr16,
+                        (FAR const union ip_addr_u *)addr->sin6_addr.in6_u.u6_addr16,
                         ntohs(addr->sin6_port));
 #else
+  /* There is only one network device; the port number can be globally
+   * unique.
+   */
+
   port = tcp_selectport(ntohs(addr->sin6_port));
 #endif
 
@@ -1099,19 +1105,56 @@ int tcp_connect(FAR struct tcp_conn_s *conn, FAR const struct sockaddr *addr)
    */
 
   flags = net_lock();
+
 #ifdef CONFIG_NETDEV_MULTINIC
-#if defined(CONFIG_NET_IPv4) && defined(CONFIG_NET_IPv6)
-  port = tcp_selectport(conn->domain, &conn->u, ntohs(conn->lport));
-#elif defined(CONFIG_NET_IPv4)
-  port = tcp_selectport(PF_INET, &conn->u, ntohs(conn->lport));
-#else
-  port = tcp_selectport(PF_INET6, &conn->u, ntohs(conn->lport));
+  /* If there are multiple network devices, then we need to pass the local,
+   * bound address.  This is needed because port unique-ness is only for a
+   * given network.
+   *
+   * This is complicated by the fact that the local address may be either an
+   * IPv4 or an IPv6 address.
+   */
+
+#ifdef CONFIG_NET_IPv4
+#ifdef CONFIG_NET_IPv6
+  if (conn->domain == PF_INET)
 #endif
-#else
+    {
+      /* Select a port that is unique for this IPv4 local address */
+
+      port = tcp_selectport(PF_INET,
+                            (FAR const union ip_addr_u *)&conn->u.ipv4.laddr,
+                            ntohs(conn->lport));
+    }
+#endif /* CONFIG_NET_IPv4 */
+
+#ifdef CONFIG_NET_IPv6
+#ifdef CONFIG_NET_IPv4
+  else
+#endif
+    {
+      /* Select a port that is unique for this IPv6 local address */
+
+      port = tcp_selectport(PF_INET6,
+                            (FAR const union ip_addr_u *)conn->u.ipv6.laddr,
+                            ntohs(conn->lport));
+    }
+#endif /* CONFIG_NET_IPv6 */
+
+#else /* CONFIG_NETDEV_MULTINIC */
+  /* Select the next available port number.  This is only one network device
+   * so we do not have to bother with all of the IPv4/IPv6 local address
+   * silliness.
+   */
+
   port = tcp_selectport(ntohs(conn->lport));
-#endif
+
+#endif /* CONFIG_NETDEV_MULTINIC */
+
   net_unlock(flags);
 
+  /* Did we have a port assignment? */
+
   if (port < 0)
     {
       return port;
diff --git a/net/udp/udp_conn.c b/net/udp/udp_conn.c
index 2592aa7dcab..af28a723594 100644
--- a/net/udp/udp_conn.c
+++ b/net/udp/udp_conn.c
@@ -619,7 +619,7 @@ int udp_bind(FAR struct udp_conn_s *conn, FAR const struct sockaddr *addr)
        * interfaces for receiving (Sending will use the default port).
        */
 
-      net_ipv6addr_copy(conn->u.ipv6.laddr, ipaddr->sin6_addr.in6_u.u6_addr16);
+      net_ipv6addr_copy(conn->u.ipv6.laddr, inaddr->sin6_addr.in6_u.u6_addr16);
 #endif /* CONFIG_NETDEV_MULTINIC */
     }
 #endif /* CONFIG_NET_IPv6 */